@simonpj Regarding your note "Better: just use SynAny for both cases. I think that'll be fine.", it turns out that I was just being silly. It's not wrong to pass stringTy in all cases there so that change is reverted and the original, unmodified code remains. However, do please note that if SynAny is passed instead, it gives rise to a Core Lint error on tests/rebindable/rebindable1.hs